The German published application DE 102004058128 A1 discloses a system for inspecting a disc-shaped object. The device suggested therein allows to capture the front and back of the disc-shaped object at the same time. Although the device suggested therein allows to capture the front of a wafer so that the representation of the wafer edge is also possible, this macro-representation does not allow the acquisition of high-resolution images of defects on the upper surface of the wafer edge.
The German published application DE 102004058126 A1 also reveals a device for inspecting the front and back of a disc-shaped object. Also the whole area of the wafer and thus also the wafer edge is captured. The device does not allow detailed representation or imaging of defects on the upper surface of the wafer edge either.
The automatic acquisition of defect images on the wafer edge involves the problem that defects too near the edge cannot be focused on.